Our Cups Runeth Under

A full-size cup decorated with Sentry and Alvin, shown with some seafloor rock samples. (Photo by Harry Brodsky)

Eric Mittelstaedt holds a shrunken and normal-sized Styrofoam head, because cups aren’t the only thing that we shrink. (Photo by Harry Brodsky)

My first cup shrank from a height of 9.5cm to just under 4cm. (Photo by Harry Brodsky)

A sampling of just a few of the cups we’ve made this expedition. (Photo by Harry Brodsky)

As Alvin and its three passengers sink toward the seafloor, a tiny cargo sits tucked away, out of sight. It’s a laundry bag, the kind made from cotton mesh, with a dozen or so Styrofoam cups stowed safely inside.

Each cup bears an image or design carefully drawn in brightly colored marker. Are these common household vessels being used for some kind of sampling mission? Is this a study on ocean plastics and their rate of degradation in seawater? No, the motivation for sending this picnic-lunch necessity to the bottom of the ocean is much more whimsical: they shrink.

Ten thousand feet below the ocean surface the surrounding pressure is immense. The weight of almost 4 kilometers (2.5 miles) of water bears down on the little sub 300 times greater than the atmosphere does at the surface. The pilot and two scientists are fine—they are protected by 3 inches of solid titanium. Our plastic passengers on the other hand, are subject to the crushing load of the deep sea. On purpose.

Styrofoam contains countless minuscule bubbles that contribute to its low density and excellent insulating properties. The bubbles are encased in a plastic called polystyrene. Under 300 atmospheres of pressure the bubbles are compressed into a tiny space and the framework of plastic around them is likewise squeezed.

The result? A sample from the dive that the chief scientists will let you take home (they get mad if you take their rocks); a small bit of proof that humans have reached the bottom of the ocean and a demonstration of physics in action: It illustrates the great pressure at the sea floor to children of all ages.

The Styrofoam tradition goes back to at least the 1980s, according to Dan Fornari, a Senior Scientist Emeritus at Woods Hole Oceanographic Institution and a seafloor exploration expert. Scientists make cups for themselves, friends and family, and outreach events. Fornari has shrunken hundreds of them himself and donated them to schools and museums, including the Smithsonian.

In truth, the cups are just a small part of an astonishingly elaborate operation to prepare and launch Alvin so that it can collect valuable scientific data. But the cups persist as a fun and educational shipboard activity—along with soaking first-time divers with chilled water.

There is something oddly romantic about designing a unique cup and using the ocean and Alvin to put a unique and indelible mark on it. It offers variety, color and character to each dive. And for the researchers who make the trip, the souvenir of a lifetime.

About this expedition: Popping rocks revisited

We will be using the research vessel Atlantis, the submersible Alvin, and the autonomous underwater vehicle Sentry, to find and collect samples of “popping rocks”—basaltic seafloor lavas that contain large amounts of carbon dioxide and other gases trapped in high-pressure bubbles that pop when the rocks are brought to the surface. We intend to use these rocks to understanding the composition and origin of gases in the deep earth. This project began with an expedition in 2016 that was cut short due to mechanical problems. You can still see blog posts from the first trip here, and we will continue adding to them during the 2018 expedition.